In processes such as semiconductor fabrication, precise amounts of gases or other fluids have to be delivered to a processing chamber or other facility. In some applications, a plurality of process gases or fluids may have to be delivered and processed.
In these applications, the flow ratios between the flow rates of the individual fluids and the total flow rate summed over all the fluids have to be maintained at desired set point values. Typically, this may accomplished by using multiple mass flow controllers to control the individual flow rates of each of the fluids. A related variable that needs to be controlled and maintained at a desired set point value is the pressure in the processing chamber. Controlling the flow rates and concentrations of multiple fluid lines, while at the same time maintaining the chamber pressure at a desired value, may be a challenge.
There is a need for systems and methods for controlling in a reliable and efficient manner both the pressure in a processing chamber as well as the flow ratios of multiple fluids that flow into the chamber for processing.